The present invention relates to a multiple valve apparatus which is preferably used for an industrial vehicle, such as a forklift truck, wherein a plurality of switching valve mechanisms can be stacked or attached together.
As a conventional multiple valve apparatus 100 of this kind, as shown in FIG. 8, there has been known a multiple valve apparatus which includes a priority valve mechanism 102 and a plurality of switching valve mechanisms 103 disposed on a downstream of the priority valve mechanism 102. In this multiple valve apparatus, as shown in FIG. 9, a high pressure operating oil discharged from a hydraulic pump, not shown, is received at a port P, and for example, a flow of the high pressure oil is divided by the priority valve mechanism 102, which is a constituent of the multiple valve apparatus, to a primarily flow ejected at a port PF for a steering operation, and a surplus flow thereof is guided through a parallel line 104 to reach input ports 132 of switching valves 131 built in the switching valve mechanisms 103. And, the switching valves 131 are manually operated by operating levers L, so that an actuator, such as a tilt cylinder TS, a lift cylinder LS or the like, can be driven by the aforementioned surplus flow.
On the other hand, in the forklift truck in recent years, as an added value, there have been required an automatic horizontal stop function in which a mast can be automatically stopped in a horizontal condition, and an automatic elevation stop function in which the mast is stopped at a predetermined height. Also, in the forklift truck in recent years, in order to prevent collapse of loads or overturn of the vehicle, there has been proposed a function for limiting an operation speed of the actuator in a load condition in which it is moved near a stroke end or in which a balance of the vehicle is liable to be lost.
However, in regard to these demands, it has been considered that the multiple valve apparatus with the manually operated conventional type can not be adopted. Thus, there has been developed a multiple valve apparatus with an automatically operated type by using an electromagnetic proportional valve in the switching valve mechanism.
However, these devices are of high grade, and have a disadvantage in the aspect of a cost thereof. Also, simply, there has been considered a method of unloading the discharge oil from the pump completely before the discharge oil is guided to the multiple valve apparatus. However, in this method, since the function of the priority valve mechanism is stopped while the automatic stop function is operated, there is caused an inconvenience such that a supply of the high pressure operating oil to the steering or the like is cut off.
The present invention has been made in order to solve these problems, and in view of the fact that a supply of the operating oil to each switching valve mechanism is operated through the parallel line communicating with a supply flow output port of the priority valve mechanism, and a main object of the invention is to provide a multiple valve apparatus which is provided with an urgent stop valve which is capable of disconnecting and connecting between the parallel line and a tank line, wherein in a predetermined condition where the automatic stop function is required, the urgent stop valve is opened to allow the supply of the operating oil only to the switching valve mechanism to eject by a simply structure, so that the automatic stop function for the actuator, such as a cylinder, can be achieved.
Another object of the invention is to provide a multiple valve apparatus, wherein a supply of the operating oil only to the switching valve mechanism is limited also by the simple structure, so that an automatic deceleration of the actuator, such as a cylinder, can be achieved.
Further objects and advantages of the invention will be apparent from the following description of the invention.